USU Junior Championship March'2005

J. Something Easier

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“How do physicists define prime numbers? Very easily: prime numbers are the number 2 and all the odd numbers greater than 2. They may show that this definition corresponds to the mathematical one: 3 is prime, 5 is prime, 7 is prime… 9? 9 is certainly not prime. Then: 11 is prime, 13 is prime. So 9 is the experiment mistake.”

From mathematical analysis course

Once physicist and mathematician argued how many prime numbers one needed for the purpose that their sum was equal to N. One said that it wasn’t known and the other that 3 was always enough. The question is how many.